The SAT is a standardized test meant to show schools how prepared you are for college by measuring key skills like reading comprehension, computational ability, and clarity of expression. Because so many students take the test, it also provides schools with data about how you compare to your peers nationwide.
You'll almost certainly need to take the SAT or ACT if you're applying to colleges or universities in the United States, since most require you to submit test scores with your application. Depending on where you want to apply, your ACT or SAT score can account for as much as 50% of the admission decision, so a strong standardized test score is vital.

Highlights

Instead of testing you on every math topic there is, the SAT asks you to use the math that you’ll rely on most in all sorts of situations. Questions on the Math Test are designed to mirror the problem solving and modeling you’ll do in:

College math, science, and social science courses.

The jobs that you hold.

Your personal life.

For instance, to answer some questions you’ll need to use several steps—because in the real world a single calculation is rarely enough to get the job done.